This invention relates to a process for synthesizing fluorocarbon esters. More particularly, this invention concerns itself with the development of a novel method for effecting the synthesis of perhalo or perfluoroesters which find use in a wide variety of military and space applications.
The synthesis of many simple fluorocarbon esters is extremely difficult because of the non-existence of suitable precursors. As a result, perhalo or perfluoroesters are relatively rare and their utilization as useful intermediates for a variety of chemical reactions has not been maximized even though their propensity for reacting easily and quickly in chemical synthesis procedures is well known. The most common chemical reaction for synthesizing esters utilizes the combination of an acid and an alcohol. Unfortunately, this simple and well known procedure cannot be utilized due to the fact that primary and secondary perfluoroalcohols are not stable. They decompose spontaneously through the elimination of hydrogen fluoride as demonstrated by the following reaction: ##STR1## in which R.sub.f represents a perfluoroalkyl groups. All fluoroalcohols with a fluorine on the same carbon as the hydroxyl group are unstable due to HF elimination. Additionally, fluorinated esters of the type R.sub.f CO.sub.2 CFR.sub.f 'R.sub.f " which contain fluorine on the alkoxy .alpha.--carbon are unstable in the presence of a fluoride ion at -78.degree. or higher. Accordingly, these compounds cannot be formed by the reaction of perfluoroalkoxides with appropriate species such as acyl fluorides. The need for a simple and efficient process for producing fluorocarbon esters in order to take maximum advantage of their utilization as reaction intermediates, therefore, become obvious. Consequently, a considerable research effort has been undertaken in an attempt to provide a convenient route to the synthesis of simple perhalo esters. As a result of this effort, a novel, route for synthesizing these potentially very useful perhaloesters has been found. The route utilizes perfluoroacyl hypohalites as a novel reactant and involves reacting a fluorocarbon acid or its derivatives with a halogen fluorosulfate at subambient temperatures of about -20.degree. or lower to produce an intermediate acyl hypohalite. This intermediate material is a reactive, positively polarized halogen species which will add to olefins readily in high yield to produce fluorocarbon esters. The resulting esters are thermally stable liquids useful as fluorocarbon solvents and fluids. They also find application as precursors to the preparation of the respective fluorocarbon ethers which are known to be fluids characterized by excellent high and low temperature properties.